(C-8), the chromosomes did not exhibit heteropycnosis 
might indicate that this feature is in some way controlled 
by the genotype. It is well known that several facets 
of chromosome form and behavior are under genotypic 
control (Rees, 1961; Chaganti, 1965). Knobs occur on 
the pachytene chromosomes of other members of May- 
deae, e.g., Zea and Tripsacum. In these genera, num- 
bers and positions at which knobs occur are characteristic 
features of populations. In C. Lachryma-Jobi var. typica 
collected at Coimbatore, a city in southwestern India, 
Nirodi (1955) observed five terminal and one interclary 
knobs. Ina population (C-8) of the same variety collected 
at a different location (Anatagiri in the coastal mountain 
range in southern peninsular India called the Eastern 
Ghats), we found only two terminal knobs. In yet an- 
other population (C-4a) of the same variety originating 
from a different locality in India (Assam, a hilly province 
in eastern India), we found eight knobs. The relation- 
ship of knob variation to geographic distribution of the 
populations remains to be studied. 
Non-homologous associations of centromeres and hetero- 
pycnotic regions in C. aquatica: In C, aquatica, at pachy- 
tene, non-homologous centromeres as well as non- 
homologous heteropyenotic regions are frequently asso- 
ciated (Plate LV). These associations, however, fall apart 
before diakinesis. The chromosomes of C. Lachryma- 
Jobi and C. gigantea exhibited none of these characteris- 
tics. The significance of such association is not known; 
however, it is likely that exchanges might take place in 
the associated regions and lead to reciprocal transloca- 
tions as suggested by Venkateswarlu (1958). The genome 
of C. aquatica is characterized by a degree of instability ; 
complex translocations are of frequent occurrence in 
natural populations(Venkateswarlu and Chaganti, 19738). 
Comparison of the genomes of the three species: A com- 
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